[Devel] [PATCH RHEL7 COMMIT] ms/ext4: fix xfstest generic/269 double revoked buffer bug with bigalloc

[Vasily Averin]

The commit is pushed to "branch-rh7-3.10.0-1160.31.1.vz7.181.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.31.1.vz7.181.8
------>
commit 43abf6424d766e23d9479361b852b31f02b5fbe9
Author: Daeho Jeong <daeho.jeong at samsung.com>
Date:   Tue Jun 22 21:51:22 2021 +0300

    ms/ext4: fix xfstest generic/269 double revoked buffer bug with bigalloc
    
        ms commit 9c02ac97989d
    
        When you repeatly execute xfstest generic/269 with bigalloc_1k option
        enabled using the below command:
    
        "./kvm-xfstests -c bigalloc_1k -m nodelalloc -C 1000 generic/269"
    
        you can easily see the below bug message.
    
        "JBD2 unexpected failure: jbd2_journal_revoke: !buffer_revoked(bh);"
    
        This means that an already revoked buffer is erroneously revoked again
        and it is caused by doing revoke for the buffer at the wrong position
        in ext4_free_blocks(). We need to re-position the buffer revoke
        procedure for an unspecified buffer after checking the cluster boundary
        for bigalloc option. If not, some part of the cluster can be doubly
        revoked.
    
        Signed-off-by: Daeho Jeong <daeho.jeong at samsung.com>
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 fs/ext4/mballoc.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 245e673..c8935c4 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4723,22 +4723,11 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
 	ext4_debug("freeing block %llu\n", block);
 	trace_ext4_free_blocks(inode, block, count, flags);
 
-	if (flags & EXT4_FREE_BLOCKS_FORGET) {
-		struct buffer_head *tbh = bh;
-		int i;
-
-		BUG_ON(bh && (count > 1));
+	if (bh && (flags & EXT4_FREE_BLOCKS_FORGET)) {
+		BUG_ON(count > 1);
 
-		for (i = 0; i < count; i++) {
-			cond_resched();
-			if (!bh)
-				tbh = sb_find_get_block(inode->i_sb,
-							block + i);
-			if (!tbh)
-				continue;
-			ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
-				    inode, tbh, block + i);
-		}
+		ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
+			    inode, bh, block);
 	}
 
 	/*
@@ -4783,6 +4772,19 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
 			count += sbi->s_cluster_ratio - overflow;
 	}
 
+	if (!bh && (flags & EXT4_FREE_BLOCKS_FORGET)) {
+		int i;
+
+		for (i = 0; i < count; i++) {
+			cond_resched();
+			bh = sb_find_get_block(inode->i_sb, block + i);
+			if (!bh)
+				continue;
+			ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
+				    inode, bh, block + i);
+		}
+	}
+
 do_more:
 	overflow = 0;
 	ext4_get_group_no_and_offset(sb, block, &block_group, &bit);